Nickel peroxide oxidizing agents have been generally described in U.S. Pat. No. 3,226,390 of Nakagawa et al. In this patent, the nickel peroxide formed by treating a nickel salt with an alkali hypohalite or persulfate has been disclosed as being particularly useful for oxidizing an unsaturated alcohol to the corresponding carbonyl compound. For example, it has been reported by Nakagawa et al. that vitamin A alcohol was oxidized with their nickel peroxide to vitamin A aldehyde under laboratory conditions in yields of 79%.
Problems have been encountered however in preparing and using nickel peroxide oxidizing agents outside of the laboratory. Nickel peroxide oxidizing agents have been found, for example, when prepared in bulk, by treating a nickel salt with an alkali hypohalite or persulfate, to coagulate on drying into impractically large aggregates. In this regard, it has been found that the consistency and selectivity of oxidations with nickel peroxide depend to a large extent upon using a fine and uniform nickel peroxide powder. As a result, the commercial preparation of efficient and selective nickel peroxide oxidizing agents has heretofore involved costly and time consuming operations to convert the nickel peroxide aggregates, as formed, to a suitable, fine, free-flowing form.
Furthermore, large scale oxidations utilizing heretofore available nickel peroxide oxidizing agents, formed by treating nickel salts with an alkali hypohalite or persulfate, have been difficult to control. Over-oxidation of unsaturated alcohol starting materials has been a frequently encountered problem. This has resulted, for example, in the formation of relatively large amounts of acids and other by-products, rather than carbonyl compounds, from the oxidation of unsaturated alcohols. Yields have fluctuated widely and have been generally inferior to the yields obtained in the laboratory.
There has been a need therefore for an improved nickel peroxide oxidizing agent which provides consistently high yields and which does not require costly treatment to convert it to a suitably fine, free-flowing form.